Fabrication and test of high-performance wide-angle lens assemblies for ocean color monitor

Abstract

REOSC has supplied Indian Space Research Organization in 1998 and 1999 with two sets of eight lens assemblies to be used for the Ocean Color Monitor mission. First set will be launched on the Indian earth observation satellite IRS P4 during 1999. All lenses have a 20mm focal length and work with a very wide field of view angle. Each set of lenses covers the visible range using eight narrow spectral bands, one for each lens, distributed from 412nm to 865nm. The eight lenses of one set are matched for perfect registration: focal length better than +/- 0.01 percent, image format better than +/- 2 micrometers , distortion better than +/- 0.45 micrometers for each point of the field. In order to achieve these very tight requirements, REOSC has developed a specific spheroparabolic lens and particularly the process allowing to polish the parabolic surface with a very repetitive quality. A method has been settled to achieve the matching specifications of the lens assemblies by iterative correction of the optical design during the testing activities. The paper discusses the main points of these topics, reports this optical fabrication and testing challenge and presents the final obtained performances.